Measuring Methane Production Research Articles

Measuring Biomethane Potential of Food Scrap Waste Anaerobically Co-Digested with Waste-Activated Sludge Using Respirometry.

The use of respirometry to study the biokinetics of microbiota treating wastewater or digesting wastewater sludges has become more prevalent over the last few decades. The use of respirometry to examine the biokinetics of anaerobic microbiota co-digesting organic waste streams such as wastewater sludge and food scrap is an area of active research. To date, no visualized protocol has been published on the topic. Accordingly, in this protocol, we configured a respirometer to measure methane production and flow rate over time using three different food-to-microorganism (F:M) ratios and food scrap waste and waste-activated sludge as substrates. The resulting data, coupled with substrate utilization measurements, provides the basis for understanding how different substrate concentrations influence the rate at which anaerobic microbiota produce methane. Additionally, this protocol presents a method to develop biokinetic parameters (e.g., methane production rate constant and yield). Others can use this respirometry protocol to examine organic degradation under anaerobic conditions and develop microbial parameters.

PSII-1 Determining Appropriate Numbers and Times of Daily Measurements to Estimate Ruminal Methane Emission of Meat Goats Using a Greenfeed System

Abstract The study was conducted to determine appropriate numbers and times of daily measurements to estimate methane production by meat goats using a GreenFeed (GF) system. Sixteen Boer wethers with an initial age of 7.4 ± 0.08 months and BW of 20.02 ± 0.71 kg were situated in a 12.4 × 12.4 pen. Oat hay, which was the major dietary constituent, was offered twice daily in individual Calan Gate feeders. Concentrate-based pellets were used as bait feed to attract animals to visit the GF regularly. The system was programed using C-Lock Inc. software to automatically dispense a small amount of pellets (120 g/day) and to measure methane production using sensors in the system. Each animal had a unique RFID tag identified by RFID reader in the system. There were 3, 4, and 6 equally spaced 1-h feeding and measurement periods (i.e., 0600-0700, 1400-1500, and 2200-2300 h for GF-3T, 0700-0800, 1300-1400, 1900-2000, and 0100-0200 h for GF-4T, and 0800-0900, 1200-1300, 1600-1700, 2000-2100, 0000-0100, and 0400-0500 h for GF-6T, respectively). The study was a Latin square with each feeding period assigned to each animal for a 2-wk period. Data were analyzed with mixed model procedures of SAS. Methane emission in g/day and g/kg dry matter intake (DMI) were not impacted by feeding period (P > 0.05). When expressed in g/min, g/visit, and g·visit-1·min-1, differences in CH4 production between feeding schedule were significant (P < 0.02). The GF-6T treatment resulted in greatest emission of CH4 in g/min (5.7, 5.9, and 6.6 for GF-3T, GF-4T, and GF-6T, respectively; P < 0.04). On the other hand, CH4 emission in g/visit ranked (P < 0.05) GF-3T > GF-4T > GF-6T (12.8, 10.9, and 7.3, respectively). Regarding CH4 intensity (g/kg BW), the differences between treatments were not significant (1.10, 1.17, and 1.16 for GF-3T, GF-4T, and GF-6T, respectively; P = 0.24). Heat production (MJ/day), which was calculated from CH4, CO2, and O2 production, was greater (P < 0.05) for GF-3T (8.1) than for GF-6T (7.6), with that for GF-4T intermediate (7.6; P > 0.05). Animals of GF-3T, GF-4T, and GF-6T visited the GF 2.1, 2.8, and 3.8 times per day, which significantly (P < 0.001) differed from each other. Average visit length was similar for GF-3T and GF-4T (P > 0.05) and greater (P < 0.05) than for GF-6T (4.6, 4.6, and 4.1 min for GF-3T, GF-4T, and GF-6T, respectively). In conclusion, results of the study indicate that at least 3 daily feeding or measurement periods should occur between 0600 and 0700, 1400 and 1500, and 2200 and 2300 h to accurately estimate methane production using a GF system in a confinement setting.

Penanganan kembali slurry keluaran digester biogas dengan substrat awal manure sapi perah dan biji pepaya untuk meningkatkan produksi methan

Co-substrate of papaya seeds (PS) with dairy cow manure (DCM) resulted an increase of organic matter (OM) content and not all OM could be digested properly in the continuous digester. This research was conducted to measure methane production of slurry that study. The experiment used MSP, BP, NaOH, batch type digester with completely randomized design. The treatments were R1 (100% DCM), R2 (95% DCM and 5% PS non germination) and R3 (95% DCM and 5% PS germination) with 5 replications. Data were analysed using analysis of variance. The observed variables were methane production, pH value, dry matter reduction (DMR) and OM reduction (OMR). Methane production showed significantly different (P<0.05), namely: 5.28; 7.19 and 6.26 l/l for R1, R2 and R3. The limited hydraulic retention time of substrate in continuous digester caused not all of the OM in R2 and R3 to be properly digested and is still left in the slurry. The decrease methane production of R3 than R2 was due to better nutrient content of R2 so that it was digested better while in the continuous digester. The higher DMR, OMR and methane production in R2 and R3 than R1 indicate that the use of BP as a co-substrate with DCM can increase the OM content and its quality and some of OM is still left in the slurry.

Smoothing spline assessment of the accuracy of enteric hydrogen and methane production measurements from dairy cattle using various sampling schemes

Estimating daily enteric hydrogen (H2) and methane (CH4) emitted from dairy cattle using spot sampling techniques requires accurate sampling schemes. These sampling schemes determine the number of daily samplings and their intervals. This simulation study assessed the accuracy of daily H2 and CH4 emissions from dairy cattle using various sampling schemes for gas collection. Gas emission data were available from a crossover experiment with 28 cows fed twice daily at 80% to 95% of the ad libitum intake, and an experiment that used a repeated randomized block design with 16 cows twice daily fed ad libitum. Gases were sampled every 12 to 15 min for 3 consecutive days in climate respiration chambers. Feed was fed in 2 equal portions per day in both experiments. Per individual cow-period combination, generalized additive models were fitted to all diurnal H2 and CH4 emission profiles. Per profile, the models were fitted using the generalized cross-validation, REML, REML while assuming correlated residuals, and REML while assuming heteroscedastic residuals. The areas under the curve (AUC) of these 4 fits were numerically integrated over 24 h to compute the daily production and compared with the mean of all data points, which was considered the reference. Next, the best of the 4 fits was used to evaluate 9 different sampling schemes. This evaluation determined the average predicted values sampled at 0.5, 1, and 2 h intervals starting at 0 h from morning feeding, at 1 and 2 h intervals starting at 0.5 h from morning feeding, at 6 and 8 h intervals starting at 2 h from morning feeding, and at 2 unequally spaced intervals with 2 or 3 samples per day. Sampling every 0.5 h was needed to obtain daily H2 productions not different from the selected AUC for the restricted feeding experiment, whereas less frequent sampling had predictions varying from 47% to 233% of the AUC. For the ad libitum feeding experiment, sampling schemes had H2 productions from 85% to 155% of the corresponding AUC. For the restricted feeding experiment, daily CH4 production needed samplings every 2 h or shorter, or 1 h or shorter, depending on sampling time after feeding, whereas sampling scheme did not affect CH4 production for the twice daily ad libitum feeding experiment. In conclusion, sampling scheme had a major impact on predicted daily H2 production, particularly with restricted feeding, whereas daily CH4 production was less severely affected by sampling scheme.

A new equipment for continuous measurement of methane production in a batch in vitro rumen system.

A new rumen batch fermentation system that allows continuous measures of total gas (GP) and methane production (MP) was tested. The fermentation system is composed of glass bottles connected to gas counters (Ritter Apparatebau GmbH & Co. KG) and an infrared gas analyser that measures the methane concentration. The system allows direct and continuous measurement of GP and MP for accurate kinetic studies. The aim of the work was to test the rumen fermentation system and compare the GP and MP kinetics obtained. Barley meal (BM), alfalfa hay (AH), corn silage (CS), and soya bean hulls (SH) were used as substrates in four consecutive fermentation runs. Cumulative volumes of GP and MP and the percentage of methane on total GP were recorded continuously until 48 h and average values at 1 h intervals were fitted with an exponential model with a lag phase reaching a good fit (R2 > 0.992). GP and MP reached the highest plateau levels for SH (1836 and 370 ml, respectively; p < 0.01) and the lowest for AH (1000 and 233 ml, respectively). The remaining substrates showed intermediate values. MP kinetics showed a discrete lag phase (from 0.09 to 1.12 h), whereas it was equal to zero for the total GP (except for SH). The methane concentration in gas flowing increased rapidly at the beginning of fermentation (from 0.35 to 0.95 h-1 ) and reached a plateau after approximately 8-12 h. In conclusion, the rumen fermentation system evaluated generates methane data comparable to those reported in the literature and allows simple continuous measurement of methane release throughout fermentation.

Enhancing thermophilic anaerobic co-digestion of sewage sludge and food waste with biogas residue biochar

Biochar addition to anaerobic digestion systems generally improves the conversion of organic waste into methane, yet biogas residues are still unwanted byproducts that may pollute the environment. Therefore, we hypothesized that biogas residues could be recycled into new biochar. We produced biochar by heating at 500 °C the residue of anaerobic digestion of food waste. We measured methane production by adding either this residue biochar, or coconut shell biochar, or corn stalk biochar, in the anaerobic co-digestion of sewage sludge and food waste. Results show that the residue biochar produces the highest daily methane amount, of 432.2 mL per g of volatile solids, versus 377.7–386.3 mL for coconut and corn biochars. This finding is tentatively explained by the fact that the residue biochar has more basic groups, which neutralize fatty acids and, in turn, alleviates acidification. Another explanation is the higher abundance in sludge of electroactive Clostridia, Methanobacterium and Methanobrevibacter, which are known to accelerate methanation. Recyling biogas residues as biochar onsite would both decrease the amount of digestion byproducts and avoid long-distance transportation of biochar from remote biomass.

Methane production potential of pulp mill sludges: microbial community and substrate constraints.

Sludges from pulp and paper mills represent a major ecological and environmental cost, and anaerobic digestion represents a method of waste reduction and energy recovery for these mills. This study compared methane production potential and microbial communities across 11 primary- and biosludges from five pulp and paper mills using various mill processes. We measured methane production from sludges in anaerobic batch reactor experiments over 64 days. Sludges were incubated with and without added substrate to test for organic substrate limitation versus inhibition of methanogens. Initial microbial communities and changes to community composition were determined using Illumina MiSeq for metabarcoding of bacterial and archaeal 16S rRNA genes. Mean methane production potential varied greatly between sludges (0.002-79mL CH4 g-1 TS). Among primary sludges, kraft mill sludge produced more methane than other mill types. For these other mills, biosludge produced more methane than primary sludge, which had evidence of methanogen inhibition. Microbial communities and diversity were influenced by the initial community composition, and high methane production was only seen in sludges with high diversity. A number of sludges innately produced substantial methane and may be targets for further modelling and larger scale testing of anaerobic digestion.

284 Genetic Selection Through Ecofeed Index Reduces Carbon Footprint in Heifers

Abstract Efficient feed conversion by ruminants has a direct impact on the animal’s carbon footprint. The objective of this study was to determine the effect of using the EcoFeed® index by STgenetics® to reduce methane production. The EcoFeed® index is an integrated approach to genetic selection based on progeny testing of females for residual feed intake to identify animals who consume less feed while maintaining production compared to their herd mates to increase profitability and global sustainability. EcoFeed® is moderately heritable and uncorrelated with traits currently selected for in dairy cows. A dataset containing phenotypic and genomic information on 5,441 heifers was used for the analysis. Heifers were divided into low, medium and high EcoFeed® classes based on ±0.5 SD from the mean. To estimate methane emissions, 17 mathematical models were collated from the literature. All models were subjected to evaluation of performance using an independent dataset containing 458 individual-animal methane production measurements. The model recommended by Intergovernmental Panel for Climate Change had the lowest root mean square prediction error with 1% mean bias and 3.37% slope bias. This model was used to calculate emissions from low and high EcoFeed® heifers. In addition, an average of all model results was computed and used to compare different classes of heifers. Based on dietary information and feed intake, low and high EcoFeed® heifers were estimated to produce 194 and 164 g methane/d, respectively, using the selected model. Using model averages, the estimated methane production was 186 and 162 g methane/d, for low and high EcoFeed® heifers, respectively. The reduction in emission between low and high EcoFeed® classes was 12.6 to 15.4%. If savings from crop production were to be considered, there will be further reductions in the carbon footprint. Therefore, genomic selection is a powerful tool to reduce carbon footprint in ruminants.

Extreme gas production in anthropogenic fibrous sediments: An overlooked biogenic source of greenhouse gas emissions

Fibrous sediments that originated from old pulp and paper industry emissions are recognized as a potential threat to the aquatic environment because they are highly contaminated. In addition, biogenic degradation of the organic material from so-called “fiberbanks” has a high potential to produce greenhouse gases (GHG). In this study, X-ray tomography, optical sensors and gas analyzers were used to identify and quantify the gas produced and released from samples of two different fiberbanks. We show that a finer fibrous structure allows the formation of larger gas bubbles and higher gas production rates compared to coarser material composed of wood pieces. High contents of methane (average 56% to 65%) and carbon dioxide (average 18% to 20%) were measured in the gas emitted from both types of fiberbank. Measured methane production rates from the fiberbanks samples are one to three orders of magnitude higher than previously reported rates from sediments within the studied temperature range (between 0.03 and 0.51 μm CH4/h/g dw over 4.7 to 20 °C). The potential for methane and carbon dioxide production in the fiberbank volume likely present in Sweden is estimated to correspond to 7% of Sweden's total known GHG emissions for 2019. These findings show that fiberbanks have the potential to be a significant emitter of GHG.

Measurement of Enteric Methane Emissions by the SF6 Technique Is Not Affected by Ambient Weather Conditions.

Simple SummaryAlthough the SF6 technique was developed over 25 years ago with the intention that it could be used to measure enteric methane production from ruminants outdoors, no experiments have reported the influence of ambient wind speed, temperature, humidity or rainfall on the accuracy of the technique. Six different cohorts of dairy cows (40 per cohort) were kept outdoors and fed a common diet during spring in 3 consecutive years. Individual cow feed intakes and daily methane productions were measured over 5 consecutive days and an automatic weather station measured air temperature, wind speed, relative humidity and rainfall every 10 min. Regression analyses were used to relate the average daily temperature, wind speed, humidity and rainfall to the average daily dry matter intake, methane production and methane yield of each cohort of cows. It was concluded that the modified SF6 technique can be used outdoors during a range of weather conditions without a significant effect on the measurement of methane production or methane yield of dairy cows.Despite the fact that the sulphur hexafluoride (SF6) tracer technique was developed over 25 years ago to measure methane production from grazing and non-housed animals, no studies have specifically investigated whether ambient wind speed, temperature, relative humidity and rainfall influence the accuracy of the method. The aim of this research was to investigate how these weather factors influence the measurement of enteric methane production by the SF6 technique. Six different cohorts of dairy cows (40 per cohort) were kept outdoors and fed a common diet during spring in 3 consecutive years. Methane production from individual cows was measured daily over the last 5 days of each 32-day period. An automated weather station measured air temperature, wind speed, relative humidity and rainfall every 10 min. Regression analyses were used to relate the average daily wind speed, average daily temperature, average daily relative humidity and total daily rainfall measurements to dry matter intake, average daily methane production and methane yield of each cohort of cows. It was concluded that the modified SF6 technique can be used outdoors during a range of wind speeds, ambient temperatures, relative humidities and rainfall conditions without causing a significant effect on the measurement of methane production or methane yield of dairy cows.

Comparison of methane production from cattle, buffalo, goat, rabbit, chicken, and duck manure

Livestock manure is reported to be one source of methane (CH4) emission. The objective of this study was to measure methane production from several types of livestock manure. The experiment used a completely randomized design (CRD), with 6 kinds of livestock manure (cow, buffalo, goat, rabbit, chicken, and duck). Each treatment was repeated three times during 8 weeks. The research method used to measure methane production was a closed chamber method, with intervals of 5 minutes. Methane samples were analyzed using gas chromatography. The results of the study showed that during eight weeks of observation, the kinds of livestock manure significantly (p <0.05) affected methane production at weeks 3, 6, 7, and 8. In those weeks, duck manure produced the highest methane production compared to other manure. Total methane gas production during 8 weeks observation which produced by duck manure was 97.99 mg g−1. Meanwhile, the lowest methane produced by rabbit manure (2.70 mg g−1). The study concluded that duck manure produced the highest methane, conversely, rabbit manure produced the lowest methane. The characteristics of fresh manure determine the level of methane production from manure. Making biogas is the best effort in mitigating methane from manure.

Methodologies for Measuring Microbial Methane Production and Emission from Soils—A Review

Methane is an important greenhouse gas. Prediction of its long-term effect on climate changes requires understanding of the sources of its release into the atmosphere. The present work aimed to review the most widely used modern methods for measuring microbial production and emission of methane in soils, and to assess their applicability to various microbial ecosystems. A classification of methods for measuring methane production in microbial soil ecosystems is proposed, based on the basic physical and mathematical approaches to data processing for each method. Under laboratory conditions, methane production is determined by soil samples incubation and layered mass balance methods, which makes it possible to investigate the methanogenic potential of a microbial community for subsequent simulation of microbial processes; these methods, however, cannot be directly extrapolated to natural ecosystems. To determine methane production in field experiments, gradient methods are used, as well as a deep soil chamber technique developed for wetlands. Methods for measuring methane emission are described, as well as their advantages and limitations. While traditional chamber techniques are simple and therefore widely used, their implementation is limited by such factors as changes in environmental conditions caused by using the chamber, small spatial scales, and difficulties in chamber installation in some ecosystems. More recently developed micrometeorological methods are free of these limitations and provide for proper estimations of gas emissions from ecosystems even if these emissions are heterogeneous in space and time. To estimate emissions from such specific objects as landfills and livestock complexes or at large scales (regional or even global), the inverse modeling method is used.

Evaluation of squeezing pretreatment for improving methane production from fresh banana pseudo-stems

Banana pseudo-stems (BPS) are an abundant and low-lignin-content lignocellulosic biomass for methane production. However, the high-water content in BPS increases the transport costs, and the resistant structure of BPS hinders methane production. In this study, squeezing of BPS as a pretreatment was evaluated for improving anaerobic digestion (AD). After 20-d digestion, methane production from squeezed BPS was 204.2 ± 6.2 mL/(g volatile solids (VS) of feedstock), which was 41.2% more than that from untreated BPS. This increase was mainly attributed to the improvement of physical properties (e.g. water absorbing capacity) and the change in the resistant structure of BPS after squeezing, which promoted good contact between microbes and substrate during AD. The measured methane production was described using a modified Gompertz model and the results showed that anaerobic process would take less time and occur faster when pretreated BPS was used as the substrate. The energy produced during AD of squeezed BPS, after deducting the energy used by the squeezer, resulted in an energy surplus of 26.2%.

Digestive physiology of captive capybara (Hydrochoerus hydrochaeris).

The capybara (Hydrochoerus hydrochaeris), the largest living rodent, probably has a "mucus-trap" colonic separation mechanism. To test this hypothesis, we measured the mean retention time of a solute marker (MRTSolute ), 2 mm (MRT2 mm ), 10 mm (MRT10 mm ), and 20 mm (MRT20 mm ) particle markers and nutrient digestibility in adult captive capybaras (27-52 kg body mass (BM), 2-11 yr). In addition, total gut fill and the selectivity factor (MRTSolute /MRT2 mm ) were calculated, and mean faecal particle size and metabolic fecal nitrogen of captive capybaras were compared to those of free-ranging specimens. Finally, we also measured methane production in one animal. The MRT2 mm (29.2 ± 8.2 hr) was different (p < 0.01) from MRTSolute (37.0 ± 13.1 hr), MRT10 mm (36.5 ± 8.2 hr), and MRT20 mm (35.1 ± 9.6 hr). The selectivity factor (1.26 ± 0.30) was in the range considered typical for a "mucus-trap" colonic separation mechanism. The estimated total gut fill was 1.50 ± 0.37% and 1.73 ± 0.25% of BM calculated from the results of the 2-mm and 10-mm particle markers, respectively. The CH4 emission was 13.7 L/day. Captive capybaras had greater mean fecal particle size (0.44 ± 0.06 vs. 0.29 ± 0.05 mm, p < 0.001) and metabolic fecal nitrogen (65.5 ± 3.91 vs. 46.8 ± 10.5% of fecal nitrogen, p < 0.001) than free-ranging capybaras. Organic matter digestibility decreased less steeply with increasing dietary crude fiber content in capybaras as compared to published data from rabbits or guinea pigs. Accordingly, the digestive physiology of the capybara is characterized by a comparatively high fiber digestibility, with a "mucus-trap" colonic separation mechanism, allowing capybaras to thrive on forage-only diets.

Technical Note: The use of total gas collection for measuring methane production in vented in vitro systems

ABSTRACT In previous studies using Ankom GP vented in vitro systems (Ankom Technology, Macedon, NY), methane production was estimated from gas production (GP) and a single gas sample from the incubation vessel’s headspace at the end of the incubation. An accurate method requires measurement of methane in the incubation vessel’s headspace and in the gases vented over the incubation period. This research aimed to determine whether the act of collecting the gas vented from the Ankom GP system influenced the estimation by the Ankom GP system of the volume of gas produced or the composition of the gas produced. A method involving collecting gas through a long (304 cm), narrow (1 mm i.d.) gas line estimated greater GP than a control method not involving collection of gas. A method involving collecting gas through a short (22 cm), wide (4 mm i.d.) gas line did not affect headspace methane percentage or estimates of GP. It is concluded that in vitro methane production can be accurately estimated by using the Ankom GP system together with collection of vented gases into gas collection bags, but only if the Ankom GP system is connected to the gas collection bag via a short, wide gas line.

Design and construction of low-cost respiration chambers for ruminal methane measurements in ruminants

ABSTRACTRuminant animals contribute significantly to methane emissions in tropical regions. Nonetheless, there are few facilities available in those regions of the world for in vivo measurement of methane production in cattle. The aim of the present work was to describe the design, construction and operation of respiration chambers for in vivo measurement of methane production in cattle in Mexico. Locally available materials were used in the construction. Walls, roof and doors were constructed of thermic panels with two windows of acrylic at the front so the animal can be observed at all times. Chambers have an air volume of 9.97 m3. Air is drawn from the chamber at a rate of 500 L/min by the effect of mass action flow generators. Methane was measured in air samples with an infrared analyzer. Chambers operate under a slight negative pressure of around -500 Pa. Air temperature inside the chambers is kept at 23 °C with an air conditioner, while relative humidity is maintained at 55 % with a dehumidifier. Functioning of the chambers was evaluated in Bos indicus, Nelore cattle fed Taiwan grass (Pennisetum purpureum) and a concentrate (18 % crude protein), and measurements were made during runs of 23 h duration. Methane production was on average 173.2 L per day, while the emission factor was 17.48 L methane per kilogram o dry matter consumed. It concludes that this respiration facility is capable of measuring methane production accurately in cattle fed tropical rations.

Stimulation and Inhibition of Anaerobic Digestion by Nickel and Cobalt: A Rapid Assessment Using the Resazurin Reduction Assay

Stimulation of anaerobic digestion by essential trace metals is beneficial from a practical point of view to enhance the biodegradability and degradation rate of wastes. Hence, a quick method to determine which metal species, and at what concentration, can optimize anaerobic digestion is of great interest to both researchers and operators. In this present study, we investigated the effect of nickel(II), cobalt(II), and their mixture, on the anaerobic digestion of synthetic municipal wastewater. Using a volumetric method, that is, measuring methane production over time, revealed that anaerobic digestion was stimulated by the addition of 5 mg L-1 nickel(II), and cobalt(II), and their mixture in day(s). However, using a novel resazurin reduction assay, and based on its change in rate over time, we evaluated both inhibition at 250 mg L-1 nickel(II) and cobalt(II), and also the stimulatory effect of 5 mg L-1 nickel(II), and cobalt(II), and their mixture, in just 6 h. By investigating the dynamic distribution of these metals in the liquid phase of the anaerobic system and kinetics of resazurin reduction by nickel spiked anaerobic sludge, the concentration of nickel(II) on anaerobic digestion performance was profiled. Three critical concentrations were determined; stimulation starting (around 1 mg L-1), stimulation ending (around 100 mg L-1) and stimulation maximizing (around 10 mg L-1). Hence, we propose that the resazurin reduction assay is a novel and quick protocol for studying the stimulation of anaerobic bioprocesses by bioavailable essential trace metals.

Bioactive fractions from the pasture legume Biserrula pelecinus L. have an anti-methanogenic effect against key rumen methanogens

Methanogenic archaea (methanogens) are common inhabitants of the mammalian intestinal tract. In ruminants, they are responsible for producing abundant amounts of methane during digestion of food, but selected bioactive plants and compounds may inhibit this activity. Recently, we have identified that, Biserrula pelecinus L. (biserrula) is one such plant and the current study investigated the specific anti-methanogenic activity of the plant. Bioassay-guided extraction and fractionation, coupled with in vitro fermentation batch culture were used to select the most bioactive fractions of biserrula. The four fractions were then tested against five species of methanogens grown in pure culture. Fraction bioactivity was assessed by measuring methane production and amplification of the methanogen mcrA gene. Treatments that showed bioactivity were subcultured in fresh broth without the bioactive fraction to distinguish between static and cidal effects. All four fractions were active against pure cultures, but the F2 fraction was the most consistent inhibitor of both methane production and cell growth, affecting four species of methanogens and also producing equivocal-cidal effects on the methanogens. Other fractions had selective activity affecting only some methanogens, or reducing either methane production or methanogenic cell growth. In conclusion, the anti-methanogenic activity of biserrula can be linked to compounds contained in selected bioactive fractions, with the F2 fraction strongly affecting key rumen methanogens. Further study is required to identify the specific plant compounds in biserrula that are responsible for the anti-methanogenic activity. These findings will help devise novel strategies to control methanogen populations and activity in the rumen, and consequently contribute in reducing greenhouse gas emissions from ruminants.

Genomic heritabilities and genomic estimated breeding values for methane traits in Angus cattle.

Enteric methane emissions from beef cattle are a significant component of total greenhouse gas emissions from agriculture. The variation between beef cattle in methane emissions is partly genetic, whether measured as methane production, methane yield (methane production/DMI), or residual methane production (observed methane production - expected methane production), with heritabilities ranging from 0.19 to 0.29. This suggests methane emissions could be reduced by selection. Given the high cost of measuring methane production from individual beef cattle, genomic selection is the most feasible approach to achieve this reduction in emissions. We derived genomic EBV (GEBV) for methane traits from a reference set of 747 Angus animals phenotyped for methane traits and genotyped for 630,000 SNP. The accuracy of GEBV was tested in a validation set of 273 Angus animals phenotyped for the same traits. Accuracies of GEBV ranged from 0.29 ± 0.06 for methane yield and 0.35 ± 0.06 for residual methane production. Selection on GEBV using the genomic prediction equations derived here could reduce emissions for Angus cattle by roughly 5% over 10 yr.

Rumen methane output and fermentation characteristics of gramineous forage and leguminous forage at differing harvest dates determined using an in vitro gas production technique

AbstractAn in vitro rumen gas production technique was employed to determine the methane production and fermentation characteristics of Leymus chinensis and Medicago ruthenica at differing harvest dates (May 15, May 30, June 30, July 30, August 30 and September 30), which are sequential phases within a single continuous growth of two 10-year-old pastures. To quantify the rate of degradation and compare in vitro rumen fermentation characteristic, a logistic-exponential model, where initial gas volume was zero (LE0), was used to fit gas production and methane output results. Dried, milled forage samples were incubated in vitro for 72 h at 39°C and gas production was recorded intermittently throughout the incubation and gas samples were collected to measure methane production. Results showed that there were significant interactions between species and harvest for all chemical composition variables (P<0.001) and condensed tannin content (P<0.001). L. chinensis produced more total gas and methane than M. ruthenica (P<0.001). Both total gas and methane production decreased lineally (P<0.001) with advancing harvest date. The degradation rates of L. chinensis and M. ruthenica harvested on September 30 were lower than those on the other harvest dates (P<0.01). M. ruthenica fermented fluid had higher concentration of ammonia N (P<0.05) and molar proportions of isobutyrate (P<0.01), valerate (P<0.001) and isovalerate (P<0.01) in total volatile fatty acids than L. chinensis. Furthermore, concentration of isovalerate decreased cubically with advancing harvest date (P<0.05). In conclusion, M. ruthenica produced less methane than L. chinensis and the total gas and methane production decreased with advancing harvest date for both species, which may be due to the changes in contents of chemical compositions and condensed tannin in forages.